After Cascade Locks, the Herman Creek/Wyeth Rd. is nice & quiet (tho a bit of a climb) - that'll keep you off I-84 until Wyeth. From there you're on I-84 (tho i think there's a path you can follow for a few miles at Starvation Creek.
the freeway has a big shoulder (eastbound, I've never ridden it westbound) but it's noisy (you know that).

From Hood River to the Dalles the State trail is really nice, as is the old highway over Rowena Crest that'll take you on in to the Dalles.